Bone cell calcium regulation will be studied using characterized isolated bone cell populations. Cells will be isolated from newborn rat calvaria by sequential digestion with collagenase. Calcium transport will be studied with Ca45. The effects of agents which affect bone function and resorption will be tested in cells characterized as either osteoclasts or osteoblasts. The relationship of calcium transport and cyclic AMP production will also be studied. Bone cell calcium regulation and cyclic AMP production will also be investigated in characterized cells from microphthalmic osteopetrotic mice to determine if this deficiency of resorption results from changes in these parameters. The information obtained in this study should elucidate the role of calcium and cyclic AMP in the control of bone metabolism and give a clearer understanding of the biochemical processes involved in the formation and resorption of bone.